Telephone system.



6.0. EDWARDS.

TELEPHONE SYSTEM.

APPLICATION FILED JAN. 4. 191ey M Imn/0r 6em/ge fawn/d5 VIIIIIIIII/IL'ISIIIIIIII G. D. EDWARDS..

TELEPHONE SYSTEM.

APPLICATION FILED IAN.4. I9I8 @e @rye Edu/dra@ Y iM/M: Aff) UNITED STATES PATENT OFFICE.

GEORGE D. EDWARDS, OF EAST ORANGE, NEW JERSEY, ASSIGNOR TO WESTERN ELEC- TRIC COMPANY, INCORPORATED, OF NEW YORK, N. `Y., A CORPORATION OF NEW YORK.

Specification of Letters Patent.

Patented Feb. 4, 1919.

Application tiled January 4, 1918.l Serial No. 210,250.

To all whom, t may concern:

Be it known that I, GEORGE D. EDWARDS, a citizen of the United States, residing at East Orange, in the -county of Essex and State of New Jersey, have invented certain new and useful Improvements in Telephone Systems, of which the following is a full, clear, concise, and exact description.

This invention relates to telephone systems and more particularly to those in which various numbers of stations may be connected together simultaneously.

. In systems of this character it is desirable to arrange the circuits so as to provide telephonie transmission which is uniform in character for the individual subscribers stations, irrespective of the number of such stations which may be interconnected during a particular period. This result is of special importance where it is essential that the efficiency of the transmission at each station be maintained at a certain excellence in order to overcome the effect of external sounds surrounding the individual station, such as are prevalent in factories, mines, etc.

Une object of the present invention is to provide a simple and inexpensive arrangement of apparatus, whereby the efficiency of the transmission between a plurality of connected stations will not be materially affected by variations 1n the number of the stations involved.

To obtain this object in accordance with one feature of the invention, a portion of the winding of a retardation or impedance coil is normally bridged across each line during the periods of non-use, while the complete winding is included in a bridged circuit in parallel with the receiver when the station is employed for listening purposes only.

Another object of the invention is to provide a system in which the transmission efficiency will not be materially affected by the association or dissociation cfa transmitter and its respective line circuit. To accoml plish this purpose, the invention cont-emplates the provision of a resistance winding effectively included in circuit during the dissociation of the transmitter from its line circuit and effectively removed from circuit during the association of the transmitter with such line circuit; the resistances of the winding and of the transmitter being so proportioned that the resistance of the system remains substantially constant irrespective of the lassociation or dissociation of the transmitter relative to the line circuit.

These and other features not specifically mentioned above will more clearly appear from the following specification and the accompanying drawings, in which Figure 1 illustrates diagrammatically one form of system embodying the present invention and in which Fig. 2 illustrates another system also embodying the invention, but modified somewhat from the system shown in Fig. 1.

In the accompanying drawings, whereinV like parts are identified by like reference characters, lines A, B and C are shown as representative ofy a large number of lines equipped with substation apparatus extending from a central ofiice D and as terminating in jacks 1 at the various'stations. For each of the lines and adapted for connecting therewith as indicated for lines A, B and C, there is shown -a subscribers telephone .set E which maybe of a suitable portable type, and at the central office D the lines are shown as beingarranged so that not only any number of those lines normally comprising a group may be connected together, but also the various groups may be joined together as desired. Inasmuch as the signaling of the various stations or of the central ofiice may be accomplished by means of any ordinary method and does not form a part of the invention, no signaling means has been shown on the drawing; also, for the same reason, the telephone circuit provided for the use of the operator at the central oice is not illustrated. It may be assumed that an operators telephone set of any usual type is furnished, any suitable means being supplied for connecting such set to the group conductors 17, 18 or 19, 20, or if desired any one of the lines and its associated telephone set may be employed for this purpose and suchV line may be connected to the proper group conductors by the closure of the associated switch 10.

It is thought that the invention may be more readily understood from a description of its operation, assuming first that the central oflice operator desires to communicate with all of the stations on the lines forming a Iparticular group, in which lines A and `B. are included. The line switches 10 of such lines are closed; the various stations are signaled b suitable means; and the operators telep one set (not shown) if'used is 110 suitably connected across group conductors 17 and 18. Prior to the response by a sta 'tion the circuit conditions in the system blade and lower middle contact of switch 10,

winding 12 of retardation coil 18, bus confdu'ctor 16 to the other terminal of battery 14.

At the same time it will be seen that through i the closing of switch 10, the operators telephone set which is not shown, but which may be used is also placed acrossI the tip and ring of the line B, since it has been assumed that such a set is connected to conductors 17 and 18.

Some of the stations will immediately respond as indicated for line A, in which ca se, as will be noted in the systems shown 1n Fig. 1, contact 2 of jackl is opened.

Invthe system shown in Fig. 2, the rmg contact 2 and intermediate connection 3 are omitted so -that the closure of the circuit 10 does not in itself complete a battery circuit over the line B. The differencey resulting from the omission of these elements in the system shown on Fig. 2 will be hereinafter explained.l On station E, of line B, plug. ging in on answering, a battery circuit iden, tical with that provided on the 4plugging in of the stations E in the system shown on Fig. 1 is established. `This circuit may now be traced in both systems overline`B from battery 14 through conductor 15, winding 11 of coil 13, upper middle contact and upper blade of switch 10, the ring side of line B to the ring spring of jack 1, from whence it proceeds to the ring of plug 6, normally 4closed contact of key 9, tip of plug 6, tip

spring of jack 1, complete winding of retardation coil 4, tip side of line A, lower blade and lower middle cont-act of switch 10, winding 12 of coil 13, and conductor 16 to the other terminal of battery 14. At the same time the receiver 7 is connected across the line in parallel with the completewindthe transmitter 8 is connected across the line prior to the opening of the bridge circuit lncluding the complete winding of retardation coil 4, for the well-known purpose .of

switches 10 are opened, the plu-gs 6 are re ymoved from the jacks 1 and all of the apparatus returns to normal.

Line C is shown as being representative of the similar lines included in another group, all the lines of which are connected to group conductors 19 and 20, and the lines comprising this group may be operated in the same manner as previously described.

In case it is desired to include more than one group of lines in a common circuit, it may be accomplished Iby any suitable central oiice switching means, of. which two arrangements are indicated on the drawing.

Sets of common conductors 22, 23 and 25, 26 are each shown as normally connected to the group conductors 17, 18 and 19, 2O respectively of particular groups, while for -the other groulp conductors, switches 21 and 24 are indicated, whereby, upon the closure of the proper switch, the desired groups are interconnected. l

Another and a somewhat more flexible method employs the well known scheme followed in connection with cordless private branch exchanges. This arrangement uti-v lizes common conductors 29, 30 which are normally independent of all of the group conductors, although all sets of group conductors are-provided with switches, as 27 and 28, which will connect the lassociated group conductors 17, 18 or 19, 20 respectively to the common conductors. By the operation of the proper switches, any desired combination ofthe groups may thus be obtained.

In the system Shown in Fig. 1, the intermediate point 3 of retardation coil 4 is so selected that the direct current resistance through winding 5 when the set E is not connected to the line, is approximately the same as that of the combined parallel bridges containing the receiver 7 and the complete winding of the retardation coil 4, when the set E is connected to the line. Thus the resultant efliciency of the transmission of any line inservice is not afected by the subsequent connection or disconnec` tion of other lines; also, the resistances are so chosen that the cutting in of the transmitter and the subsequent opening of the bridge circuit containing the complete winding of the retardation coil does not materially ailect the transmission.

Inapplications of the invention wherein the number of stations connected in circuit remains substantially the same, the necessity of providing means to preserve the resultant eiiciency of transmission of any line in service irrespective of subsequent connections or disconnection oi other lines is not of such great importance. To meet these rac conditions a somewhat simpler system such as illustrated in Fig. 2 and resulting from the omission of the ring contact 2, and intermediate connection 3, will prove satisfactory. It will be observed that the retardation coil 4 is retained, however, and is normally in bridge with the receiver, but Cut out of circuit upon the depression f key 9 to substitute a transmitter in bridge with the receiver for talking purposes. The resistancesl in this system as in the system shownon Fig. 2 are so chosen that the Cutting-in of the transmitter and the subsequent opening of the bridge circuit containing ythe retardation coil 4 does not materially affect the transmission. Condensers 31 are also provided in the system shown on Fig. 2 and serve to prevent the connection of battery supply to any line except through its retardation coil 13 on closure of its switch 10; although permitting the passage of fluctuated telephonie circuits between connected stations of the system.

Wvhat is claimed is:

1. In a telephone system, a common source of current, a line connected to said source of current, a subscribers telephone set arranged for operative connection with said line, and means associated with said line for preventing a change in the total line impedance upon the operative connection of said telephone set with said line.

2. In a telephone system, a source of energy at a central point, a line extending from said central point and connected to said source, a subscribers telephone set adapted to be removably connected-with -said line, and means associated with said line for preventing a change in the total line impedance upon the association of said telephone set with said line.

3. In a telephone system, a source of energy at a central point, a line extending from said central point and connected to said source, a subscribers telephone set, means for removably connecting said telephone set with said line, and means for varying the resistance of said line upon the connection therewith of said telephone set whereby the total line impedance is substantially unchanged. i

4. In a telephone system, a source of energy at a central point a line extending from said central point VKand connected to said source, a ,subscribers telephone set,

' means ,for removably connecting said telephone set with said line, and meansassociated with said line for maintaining the drain kon the source of energy constant regardless of the association of said telephone set with said line.

5. In a telephone system, a source of energy, 'at a central point, a line extending from said central point and connected to said source, a subscribers telephone set adapted to .be removably connected with said line, and means operable upon the connection of said telephone set to alter the impedance relations existing in said line to Aconnecting said telephone sets with said lines, and means associated with each of said lines for removing an impedance Jfrom said line equivalent to that of said telephone set upon connection of said telephone set with said line.

7. In a telephone system, a source of energy at a central point, a plurality of lines adapted to be interconnected in a network supplied from said central point with energy for conversational purposes, telephone sets adapted to be associated with said lines, means individual to the lines rendered operative upon the association of a telephone set therewith for preventing a change in the electrical constants of the network, whereby the addition of a telephone set to a line of the network will notimpair the transmission between telephone sets connected to other lines in such network.

8. In a telephone system, a subsoribers station including a retardation coil having two windings, one winding of said coil normally bridged across said line, a telephone set having a normally open transmitter ciropening said bridge and including the other of said windings ofsaid retardation coil in a bridge in parallel with said receiver circuit, and means included in said telephone set for closing said transmitter circuit and subsequently opening said retardation coil bridge.

9. In a telephone system, a luralityl of lines extending from a central o ce and termi'nating in setsl of switching terminals, a source of energy at said central oice adapted for connection with said lines, means at said central oice for interconnecting said lines in groups of varying numbers, a plurality of subscribers telephone sets comprising normally closed receivercircuits and normally openitransmitter circuits and adapted for connection with said sets of switching terminals, circuit-closing means included in each of said subscribers telephone sets for completing said transmitter circuit, means included with said lines to maintain constant the etliciencyof the transmission between said telephone sets when connected to any of said connected lines independent of the connection or disconnection of others of said telephone sets with others of said lines grouped together by said interconnecting means for receiving purposes, and means included in each of said lines and controlled by said circuit-closing means for further maintaining said efficiency upon the operation of any of said telephone sets as trans? l a normally open transmitter circuit and ter minating in a plug for connection With said Jack, a retardation ,coil having a plurality of v windings,'a winding of said retardation coil connected to said Iswitching terminals to produce substantially the same effective impedance conditions as said subscribers telephone set, a second Winding of said retardation coil adapted to be included in parallel with said receiver upon the connection of said plug with said jack, -means for discon- 4 necting said firstmentioned Winding upon the inclusion yoit said second Winding, and switching means included in said su-bscribers set for closing said transmitter -circuit and removing said second'mentioned Winding when said subscribers set is to be used for transmitting purposes.

- 12. In a telephone system, a line terminat ing in a set of switching terminals, one Winding of a deuble-Wound retardation coil bridged across said line at said switching terminals, a telephone set having a transmitter and a 'receiver adapted for connection with said switching terminals, means operable upon the connection of said telephone set with said terminals for excluding said winding and substituting therefor the second winding of said retardation coil in parallel with said receiver for receiving purposes,

.and means included in. said telephone set for excluding said second Winding and including said transmitter in circuit for transmittlng purposes.

13. In a telephone system, a source of energy, a telephone line' connected to said source, a transmitter adapted to be opera-l tively connected to said line, means to control the operative connection of said transmitter with said line, and means to maintain the drain on said source of energy substantially constant regardless of the connection of said transmitter'with said line.

substantially constant regardless of the operative connection of said transmitter circuit connectlon with said llne.

15. In a telephone system, a source of encrgy, a line connected to said source, a transmitter adapted to be operatively connected With said line, compensating means having substantially the same resistance as said transmitter adapted-.to be operatively connected with said line, and means to alternatively connect said transmitter and said compensatlng means operatively with said line.

16. In a telephone` system, a source of energy, a line connected-to said source, a transmitter circuit connection adapted to be operatively connected Withsaid line, a 'transf mitter included in said transmitter circuit connection, a compensating circuit connection adapted to be operatively connected with said line, resistance means included in one of said circuit connections to render the circuit connections of substantially the same resistance, and means to alternatively connect said circuit connection operatively With said line.

17. In a telephone system, a first circuit,

` a receiver included therein, a transmitter circuit adapted to 1loe operatively connected with said first circuit, a transmitter therein, a' compensating circuit, compensatmg means therein, and means for controlling the operative: connection of said first circuit and controlling said compensating circuit; the resistances of said transmit-ter and compensating circuits being so proportioned that the resistance of the system remains substantially vconstant regardless of the operative connection of said transmitter circuit with said first circuit.

18. In a telephone system, a first circuit, a receiver included therein, a transmitter circuit adapted to' be operatively connected with said first circuit, a transmitter therein, a compensating circuit adapted to be operatively connected With said first circuit, com'- pensating means therein, and means to alterter and compensating circuits being so proadaptedto be operatively connected in parallel with said first circuit, av transmitter included in said second circuit, a third circuit adapte-d to be operatively connected in parallel with saidy first circuit, and means ineluded in one of said second and third circuits to render the resistance of said second and third circuits substantially the same; and means to alternatively connect said second and third circuits operatively in parallel with said first circuit.

" 20. In a telephone system, a first circuit, a receiver included therein, a second circuit adapted to -be operatively connected in parallel with said first circuit, a transmitter included in said second circuit, a third circuit adapted to be operatively connected in parallel with said first circuit, compensating resistance means included in said third circuit of substantially thesame resistance as said transmitter, and means controlling the operative'connection of said second and'third circuits with said first circuit.

21. In a telephone system, a first circuit, a receiver included therein, a second circuit ada ted to be operatively connected in parallei) with said first circuit, a -transmitter included in said second circuit, a third circuit adapted to be operatively connected in parallel with said first circuit, compensating resistance means included 1n said third circuit of substantially the same resistance as said transmitter, and means to alternatively connect said second and third circuits operatively in parallel with said first circuit.

In witness whereof I hereunto subscribe my7name this 28th day of December, A. D. 191

'GEORGE D. EDWARDS. 

